Dead hen

This evening, my husband found one of my Lavender Orpinton hens dead in the coop beside the water container with an egg sticking partly in, partly out. He said it looked normal sized and could not see any indication of any injuries. Since I have several chickens (hens and three roosters) of different breeds, I am not sure if she was the hen that laid an unusually large egg two days ago (picture posted on separate thread). I originally thought that one of my Jersey Giants must have laid the huge egg, but yesterday one of my Golden Laced Wyandottes had a bloody rump and there was an egg streaked with blood/ No evidence of prolapse on any of my hens yesterday, including the Wyandotte or the Lavender. The egg in question from two days ago weighs 4 ounces. So it is HUGE! I don't know which hen laid it, as I said, but I'm not sure what killed my Lavender hen. She was about eight months old and has been laying, I am sure, with no previous problems. Since she was in the coop, there is no evidence of a prolapse, and the partially-laid egg was of normal size today, anyone have any ideas? I am so sad that my little Lavender died and hope I did not miss something that could have saved her.